Display device and method of making display device

ABSTRACT

A display device with increased lifespan is presented. The device includes a plurality of thin film transistors, a passivation layer formed on the thin film transistors, a plurality of pixel electrodes formed on the passivation layer and electrically connected to the thin film transistors, and a wall dividing the pixel electrodes. The wall has a main section and an auxiliary section that is lower than the main section. A caved-in section is disposed between the main section and the auxiliary section. An organic layer is formed on the pixel electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application of U.S. patent application Ser. No.11/502,933, filed Aug. 11, 2006, which application claims the benefit ofKorean Patent Application No. 2005-0073741 filed on Aug. 11, 2005 in theKorean Intellectual Property Office, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device, and more particularlyto a display device with a substantially flat organic layer.

2. Description of the Related Art

Among different types of flat panel displays, organic light emittingdiode (OLED) has become popular due to its desirable characteristicssuch as low driving voltage, slim design, light weight, a wide viewingangle, and a quick response time. OLED is generally classified into apassive-matrix type and an active-matrix type depending on the drivingmethod. In the active-matrix OLED, each thin film transistor thin filmtransistor is connected to a pixel area to control the organiclight-emitting layer's emission by pixel areas. A pixel electrode isdisposed in a pixel area and electrically separated from the adjacentpixel electrodes so that it can be driven independently. A wall higherthan the pixel electrode is formed between the pixel areas to preventthe pixel electrodes from being short-circuited or accidentally couplingmultiple pixel areas. On the pixel electrodes between the walls, ahole-injecting layer and the organic light-emitting layer are formedsequentially.

Where the hole-injecting layer and the organic light-emitting layercontain a polymer, they are usually formed by an ink-jet method.However, ink-jet method does not always result in the optimal layers.For example, the thickness of the hole-injecting layer and the organiclight-emitting layer around the wall is greater than desired when thelayers are formed with the ink-jet method. This excessive thicknessaround the wall compromises the uniformity of brightness and reduces thelifespan of the display.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide adisplay device in which an organic layer is substantially flat. Anotheraspect of the present invention is to provide a method of making adisplay device in which an organic layer is substantially flat.

The foregoing and/or other aspects of the present invention are alsoachieved by providing a display device. The display device includes aplurality of thin film transistors, a passivation layer formed on thethin film transistors, a plurality of pixel electrodes formed on thepassivation layer and electrically connected to the thin filmtransistors, and a wall dividing the pixel electrodes. The wall has amain wall and an auxiliary wall that is lower than the main wall. Acaved-in part is disposed between the main wall and the auxiliary wall.An organic layer is formed on the pixel electrodes.

The foregoing and/or other aspects of the present invention are alsoachieved by providing a method of making a display device. The methodentails providing a plurality of thin film transistors and a passivationlayer on an insulating substrate, providing a plurality of pixelelectrodes electrically connected to the thin film transistors on thepassivation layer, forming a wall dividing the pixel electrodes, andforming an organic layer on the pixel electrodes. The wall has a mainwall and an auxiliary wall that is lower than the main wall. A caved-inpart is disposed between the main wall and the auxiliary wall.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages of the present inventionwill become apparent and more readily appreciated from the followingdescription of the exemplary embodiments, taken in conjunction with theaccompanying drawings of which:

FIGS. 1A and 1B illustrate a problem with the conventional method when apolymer solution is dried;

FIG. 2 is a sectional view of a display device according to a firstembodiment of the present invention;

FIGS. 3A through 3H are sectional views to illustrate a method of makinga display device according to the first embodiment of the presentinvention;

FIG. 4 is a sectional view to illustrate another method of making adisplay device according to the first embodiment of the presentinvention; and

FIG. 5 is a sectional view of a display device according to a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals refer to likeelements throughout. The embodiments are described below to explain thepresent invention by referring to the figures.

First, a problem when a polymer solution is dried will be described withreference to FIGS. 1A and 1B.

When making a display device, a polymer is dissolved in a solvent tomake a polymer solution, and then an organic layer is formed bydepositing the polymer solution with an ink-jet method. The organiclayer, for example, is used as a hole-injecting layer or alight-emitting layer of an OLED and may have tens to hundreds of nm ofthickness.

FIG. 1A shows that a polymer solution 200 is dropped on an insulatingsubstrate 100, and FIG. 1B shows that the solvent is removed from thepolymer solution 200 to form the organic layer 201.

The polymer solution 200 has a dome shape—i.e., it is thicker in themiddle than at the edge due to its surface tension. Vapor density of thesolvent is higher in the middle than at the edge. Since the drying speedof the solvent is inversely proportional to the vapor density around thepolymer solution 200, the solvent dries faster at the edge than in themiddle. The polymer of the polymer solution 200 transfers to the edgewhere the solvent dries fast, and thus the organic layer 201 formedaccordingly is higher at the edge “A” than in the middle, as shown inFIG. 1B.

If the organic layer 201 has the shape shown in FIG. 1B, its lifespan isdecreased as well as its aperture ratio, and the brightness differencebetween the edge and the middle of the organic layer 201 increases.

Various techniques have been tried to avoid the problem of uneventhickness in the organic layer 201. For example, the polymer solution200 was prepared using a low-solubility solvent and dried at a hightemperature. When dried at high temperature, the polymer solution driesquickly to obtain a comparatively flat organic layer. However, thelifespan and efficiency of the organic layer 201 are still negativelyaffected.

When the polymer solution is prepared using a solvent having lowsolubility, the polymer becomes a gel that interferes with migration ofthe polymer molecules to the edge. Thus, a comparatively flat organiclayer is obtained. However, the polymer solution easily turns into a gelduring storage and transport.

To solve this problem, the present invention changes the structure ofthe wall where the polymer solution is disposed.

FIG. 2 is a sectional view of a display device according to a firstembodiment of the present invention.

A display device 1 according to the present invention includes a thinfilm transistor (TFT) formed on an insulating substrate 10, a pixelelectrode 32 electrically connected to the thin film transistor 20, awall 40 between the pixel electrodes 32, an organic layer 50 formed onthe pixel electrode 32 and a common electrode 61 formed on the organiclayer 50.

In the first embodiment, the thin film transistor is made of amorphoussilicon. However, this is just an exemplary embodiment and not alimitation of the invention. Other types of thin film transistors, suchas a thin film transistor made of polysilicon, would also be within thescope of the invention.

The display device according to the first embodiment will now bedescribed.

A gate electrode 21 is formed on the insulating substrate 10 whichcontains an insulating material such as glass, quartz, ceramic, orplastics, among others.

A gate insulating layer 22 containing silicon nitride (SiNx) or the likeis formed on the insulating substrate 10 and the gate electrode 21. Asemiconductor layer 23 of amorphous silicon and an ohmic contact layer24 of n+ hydrogenated amorphous silicon highly doped with n-type dopantare formed sequentially on the gate insulating layer 22 where the gateelectrode is disposed. Here, the ohmic contact layer 24 is divided intotwo parts with respect to the gate electrode 21.

A source electrode 25 and a drain electrode 26 are formed on the ohmiccontact layer 24 and the gate insulating layer 22. The source electrode25 and the drain electrode 26 are separated from each other by a gapabove the gate electrode 21.

A passivation layer 31 is formed on the source electrode 25, the drainelectrode 26, and parts of the semiconductor layer 23 that are notcovered with the source electrode 25 or the drain electrode 26. Thepassivation layer 31 contains silicon nitride (SiNx) and/or an organiclayer. The passivation layer 31 has a contact hole 27 that extendsthrough it to expose the drain electrode 26.

The pixel electrode 32 is formed on the passivation layer 31. The pixelelectrode 32 acts as an anode and provides holes to the organic layer50. The pixel electrode 32 contains a transparent conductive materialsuch as indium tin oxide (ITO) or indium zinc oxide (IZO). The pixelelectrode 32 is patterned in an approximately rectangular shape in planview and is about 50 to about 200 nm thick.

The wall 40 is formed between the pixel electrodes 32. The wall 40extends between the pixel electrodes 32 to define a pixel area and isformed on the thin film transistor 20 and the contact hole 27. The wall40 prevents the source electrode 25 and the drain electrode 26 frombeing short-circuited with the common electrode 61. The wall 40 containsa photoresist having a thermal resistance and a solvent-resistingproperty, such as acrylic resin, polyimide resin or the like. The wall40 may also contain an inorganic material such as SiO₂ and TiO₂, thushaving a double-layer structure of an organic layer and an inorganiclayer.

The wall 40 includes a main wall 41 flanked by auxiliary walls 42disposed on two sides of the main wall 41. As shown, the auxiliary walls42 are lower than the main wall 41. Caved-in parts 43 are formed betweenthe main wall 41 and the auxiliary walls 42. Flat parts 44 are disposedbetween the caved-in parts 43 and the main wall 41 and extendsubstantially parallel to the pixel electrode 32. The flat parts 44 areas high as the auxiliary walls 42. During the formation of the organiclayer 50, the main wall 41 prevents adjacent organic layers 50 frommixing with each other. The caved-in parts 43 increase vapor densityaround the wall 40 to form the organic layer 50 with a uniformthickness.

The width d1 of the wall 40 is in the range of about 40 μm to about 60μM. The height d2 of the main wall 41 is in the range of about 0.5 μm toabout 5 μm, and the height d3 of the auxiliary walls 42 is in the rangeof about 0.25 μm to about 4.5 μm, or about 50% to about 90% of theheight d2 of the main wall 41. If the height d3 of the auxiliary walls42 is 50% of the height d2 of the main wall 41 or less, it is hard toachieve the depth d5 for the caved-in parts 43. If the height d3 of theauxiliary walls 42 is 90% of the height d2 of the main wall 41 or more,the inter-pixel partitioning effect of the wall 40 becomes compromisedsuch that the adjacent organic layers 50 may mix with each other duringthe formation of the organic layer 50.

The width d4 of the caved-in parts 43 is in the range of about 0.5 μm toabout 10 μm and the depth d5 thereof is in the range of about 50% toabout 300% of the width d4. If the depth d5 of the caved-in parts 43 isabout 50% of the width d4 or less, the effect of increasing the vapordensity around the wall 40 becomes weakened, and thus the organic layer50 may be formed thickly around the wall 40. If the depth d5 of thecaved-in parts 43 is 300% of the width d4 or more, the caved-in parts 43have a steep slope, and thus the common electrode 61 may bediscontinuous within the caved-in parts 43.

The organic layer 50 is formed on the auxiliary walls 42, the caved-inparts 43 and a portion of the pixel electrode 32 that is not coveredwith the wall 40. The adjacent organic layers 50 are separated by themain wall 41, and accordingly the organic layer 50 is not formed on asurface “B” of the main wall 41.

The organic layer 50 includes a hole-injecting layer 51 and alight-emitting layer 55.

The thickness d6 of the hole-injecting layer 51 is approximately in therange of about 50 nm to about 400 nm, and is preferably about 200 nm.The hole-injecting layer 51 formed on the pixel electrode 32 issubstantially uniformly thick regardless of the distance from the wall40. The thickness of the hole-injecting layer 51 formed on the auxiliarywalls 42 and the caved-in parts 43 may be different from the thicknesson the pixel electrode 32. Usually, the hole-injecting layer 51 formedon the caved-in parts 43 is thinner than the hole-injecting layer 51formed on the pixel electrode 32.

The hole-injecting layer 51, for example, may be made of poly thiophenederivatives such as poly-3,4-ethylenedioxythiophene (PEDOT) and acompound such as poly styrenesulfonate (PSS).

The light-emitting layer 55 includes a red light-emitting layer 55 a, agreen light-emitting layer 55 b and a blue light-emitting layer 55 c.The thickness d7 of the light-emitting layer 55 is approximately in therange of about 50 nm to about 400 nm, and is preferably about 200 nm.The light-emitting layer 55 formed on the pixel electrode 32 issubstantially uniformly thick regardless of the distance from the wall40. the thickness of the light-emitting layer 55 formed on the auxiliarywalls 42 and the caved-in parts 43 may be different from one on thepixel electrode 32. As with the hole-injecting layer 51 described above,the light-emitting layer 55 formed on the caved-in parts 43 is usuallythinner than the light-emitting layer 55 on the pixel electrode 32.

The light-emitting layer 55 may be made of polyfluorene derivatives,poly(p-phenylene vinylene) derivatives, polyphenylene derivatives,poly(N-vinylcarbazole) derivatives and poly thiophene derivatives orcompounds thereof doped with a perillene group pigment, rhodamine,rubrene, perillene, 9,10-diphenylanthracene, tetraphenylbutadiene, nilered, cumarine 6, quinacridone, etc.

Holes transmitted from the pixel electrode 32 and electrons transmittedfrom the common electrode 61 are combined in the light-emitting layer 55to form excitons. As is well-known, the excitons generate energy in theform of light when transitioning to a lower energy level state.

The common electrode 61 is disposed on the wall 40 and thelight-emitting layer 55. The common electrode 61 functions as a cathodeand provides electrons to the light-emitting layer 55. The commonelectrode 61 may be made of a calcium layer and an aluminum layer thatare sequentially deposited. In this case, a layer having a low workfunction is preferably disposed closer to the light-emitting layer 55than the other layer. The common electrode 61 directly contacts thelight-emitting layer 55 to inject the electrons. The common electrode 61directly contacts the surface “B” of the main wall 41.

Lithium fluoride may increase the light-emitting efficiency depending onthe material of the light-emitting layer 55. Thus, to take advantage ofthis possibility, a lithium fluoride layer may be formed between thelight-emitting layer 55 and the common electrode 61. Where the commonelectrode 61 is made of a non-transparent material such as aluminum andsilver, the light emitted from the light-emitting layer 55 exits thestructure through the insulating substrate 11. This is called abottom-emission method.

Although not shown, the display device 1 may also include an electrontransfer layer and an electron injection layer between thelight-emitting layer 55 and the common electrode 61. Moreover, thedisplay device 1 may further comprise a passivation layer to protect thecommon electrode 61 and a bag to prevent moisture and air frompenetrating into the organic layer 50. The bag may be a sealing resinand a sealing can.

As described above, the display device 1 according to the firstembodiment comprises the hole-injecting layer 51 and the light-emittinglayer 55 of uniform thickness. Accordingly, brightness becomes uniformacross the pixel area and the aperture ratio and lifespan increase.

Hereinafter, a method of making the display device according to thefirst embodiment of the present invention will be described withreference to FIGS. 3A through 3H.

Referring to FIG. 3A, the thin film transistor 20 is formed on theinsulating substrate 10. The thin film transistor 20 has a channelregion made of amorphous silicon and is manufactured by any suitableconventional method. Then, the passivation layer 31 is formed on thethin film transistor 20. The passivation layer 31 may include a layer ofsilicon nitride that is formed by a chemical vapor deposition. Thepassivation layer 31 is patterned by photolithography to form a contacthole 27 that exposes the drain electrode 26. Thereafter, ITO isdeposited by a sputtering method and patterned to form the pixelelectrode 32. The pixel electrode 32 is connected with the drainelectrode 26 through the contact hole 27.

Referring to FIG. 3B, a wall material layer 45 is formed on the pixelelectrode 32 and the passivation layer 31 and exposed. The wall materiallayer 45 may contain a photoresist and may be formed by a slit coatingmethod or a spin coating method. The wall material layer 45 is exposedwith a slit mask (not shown) to form the wall 40. An area C on the pixelelectrode 32 where the wall 40 is not formed is exposed to highintensity light and an area D where the main wall 41 is formed is notexposed to light at all. An area E where the caved-in parts 32 areformed is exposed to light having an intensity level between theintensity level used for the D-area and the intensity level used for theC-area. An area F where the auxiliary walls 42 are formed is exposed tolight having an intensity level between the intensity level used for theE-area and the intensity level used for the D-area. Although not shownin the drawings, an area where the flat parts 44 are formed is exposedwith light having an intensity level between the intensity level usedfor the D-area and the intensity level used for the E-area.

FIG. 3C shows the wall 40 that is formed after exposing the wallmaterial layer 45. The height of the wall 40 is slightly lower than thatof the wall material layer 45 since the wall material layer 45 isdeveloped to form the wall 40.

Referring to FIG. 3D, a hole-injecting solution 52, which is a polymersolution that contains a hole-injecting material, is dropped onto thepixel electrode 32 by an ink-jet method to form the hole-injecting layer51. The hole-injecting solution 52 is disposed higher than the auxiliarywalls 42 and fills the entire caved-in parts 43. Adjacent pools ofhole-injecting solutions 52 are separated by the main wall 41 so thatthey do not mix with each other. The level of the hole-injectingsolution 52 is not flat. Thus, its level is lower than the height of themain wall 41 close to the wall 40 but higher than the main wall 41 nearthe middle of a pool of the hole-injecting solution 52.

The hole-injecting solution 52 includes poly thiophene derivatives suchas poly-3,4-ethylenedioxythiophene (PEDOT), a compound such as polystyrenesulfonate (PSS) and a polar solvent where the compound isdissolved. The polar solvent, for example, comprises isopropyl alcohol(IPA), n-butanol, γ-buthylolactone, N-methylpyrrolidone (NMP) and1,3-dimethyl-2-imidazolidinon (DMI) and derivatives thereof andglycolether such as cabitol acetate, buthyl cabitol acetate or the like.

FIG. 3E shows a process for drying the hole-injecting solution 52 toremove the solvent. The drying process is performed under nitrogen atroom temperature at a pressure of 1 Torr. If the pressure is too low,the hole-injecting solution 52 may rapidly evaporate. Also, if thetemperature is higher than room temperature (e.g., standard temperatureand pressure), the evaporation speed of the solvent increases so that itis hard to form a layer uniformly. The vapor density remains constantregardless of distance from the wall 40 due to the vapor of the solventevaporating from the hole-injecting solution 52 in the caved-in parts 43during the drying process. Accordingly, the solvent of thehole-injecting solution 52 is removed at regular rate regardless of itsposition in the pool of hole-injecting solution 52, and thehole-injecting material is prevented from migrating to certain parts ofthe pool.

FIG. 3F shows that the hole-injecting layer 51 is formed after thehole-injecting solution 52 is completely dried. The hole-injecting layer51 is formed on the pixel electrode 32 with a comparatively constantthickness. The constant thickness is achieved because, as mentionedabove, the hole-injecting material does not migrate to certain positionsduring the drying process of the hole-injecting solution 52. Thehole-injecting layer 51 is also formed on the caved-in parts 43, and thehole-injecting layer 51 on the caved-in parts 43 may be thinner than thecorresponding layer on the pixel electrode 32.

After completing the drying process, heat treatment may be performedunder nitrogen, but preferably in a vacuum. The heat treatment may beperformed at a temperature of about 200° C. for 10 minutes, so that anysolvent or water remaining in the hole-injecting layer 51 is removed.

Referring to FIG. 3G, a light-emitting solution 56, which is a polymersolution containing a light-emitting material, is dropped on the pixelelectrode 32 where the hole-injecting layer 51 is formed in order toform the light-emitting layer 55. The light-emitting solution 56 isdisposed to a level higher than the auxiliary walls 42 and fills theentire caved-in parts 43. Adjacent light-emitting solutions 56 areseparated by the main wall 41 so that they do not mix with each other.The light-emitting solution 56 is disposed lower than the main wall 41close to the wall 40, but higher than the main wall 41 far from the wall40.

The light-emitting solution 56 contains a nonpolar solvent that does notdissolve the hole-injecting layer 51, so that the hole-injecting layer51 remains substantially intact even if it comes in contact with thelight-emitting solution 56. The nonpolar solvent may becyclohexylbenzene, Dehydrobenzofuran, trimethylbenzene, ortetramethylbenzene, among others.

The hole-injecting layer 51 does not have a chemical affinity to thenonpolar solvent. Thus, the light-emitting layer 55 may not adhereclosely to the hole-injecting layer 51 or may not be applied uniformlyin case of using the light-emitting solution 56 containing the nonpolarsolvent.

To increase the chemical affinity of the hole-injecting layer 51 to thenonpolar solvent, a surface reforming process is performed on thehole-injecting layer 51 before dropping the light-emitting solution 56.

During the surface reforming process, a surface reforming agent isapplied to the hole-injecting layer 51, and then dried and evaporated.The surface reforming agent may be cyclohexylbenzene, Dehydrobenzofuran,trimethylbenzene and tetramethylbenzene, which are the solvents of thelight-emitting solution 56, or toluene and xylene which are similar tothe solvent. The surface reforming agent may be applied by an ink-jetmethod, a spin coating method or a dip-coating method.

A surface of the hole-injecting layer 51 becomes chemically attractiveto the nonpolar solvent through the surface reforming process, so thatthe light-emitting solution 56 may be uniformly applied.

FIG. 3H shows that the light-emitting layer 55 is formed after thelight-emitting solution 56 is completely dried. The drying process forthe light-emitting solution 56 is substantially the same as of thedrying process for the hole-injecting solution 52 described above. Thelight-emitting layer 55 is formed on the pixel electrode 32 with acomparatively constant thickness since the light-emitting material doesnot migrate in the drying process of the light-emitting solution 56. Thelight-emitting layer 55 is also formed on the caved-in parts 43 and maybe thinner than one on the pixel electrode 32.

Thereafter, the common electrode 61 is formed on the light-emittinglayer 55, and then the display device 1 as shown in FIG. 2 is completed.

Hereinafter, another method of making the display device according tothe first embodiment of the present invention will be described withreference to FIG. 4. In this method, the wall 40 is formed by an imprintmethod.

FIG. 4 shows that the wall material layer 45 is deposited on the pixelelectrode 32. A wall forming mold 300 comprising a reverse pattern ofthe wall 40 is provided over the wall material layer 45. The wallforming mold 300 is pressed into the wall material layer 45 such thatthe wall material layer 45 fills the pattern of the wall forming mold300 and the remainder is removed from the pixel electrode 32. The wallforming mold 300 may include a through hole (not shown) so that theextra wall material layer 45 can be removed. Then, the wall forming mold300 is removed to leave the wall 40.

FIG. 5 is a sectional view of a display device according to a secondembodiment of the present invention. A difference between the firstembodiment and the second embodiment is as follows.

A wall 40 according to the second embodiment does not include a flatpart 44 like the first embodiment. Thus, a main wall 41 is directlyconnected to the caved-in parts 43.

In the display device 1 a according to the second embodiment, anintermediate layer 58 is formed between the hole-injecting layer 51 andthe light-emitting layer 55. The intermediate layer 58 holds electronsfrom the light-emitting layer 55 so that they are not injected into thehole-injecting layer 51. Accordingly, the hole-injecting layer 51,especially the hole-injecting layer made of PEDOT, is properly protectedto increase the lifespan of the display device. The intermediate layer58 is formed by an ink-jet method the same way as the hole-injectinglayer 51 and the light-emitting layer.

As described above, the present invention provides a display devicehaving a substantially flat organic layer.

Also, the present invention provides a method of making a display devicewith a substantially flat organic layer.

Although a few embodiments of the present invention have been shown anddescribed, it will be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe appended claims and their equivalents.

1. A display device comprising: a plurality of thin film transistors; apassivation layer formed on the thin film transistors; a plurality ofpixel electrodes formed on the passivation layer and electricallyconnected to the thin film transistors; a wall dividing the pixelelectrodes, the wall having a main wall and an auxiliary wall that islower than the main wall; and an organic layer formed on the pixelelectrodes.
 2. The display device according to claim 1, wherein theorganic layer formed on the auxiliary wall is thinner than the organiclayer on the pixel electrode.
 3. The display device according to claim2, wherein the height of the auxiliary wall is about 50% to about 90% ofthe height of the main wall.
 4. The display device according to claim 3,wherein the height of the auxiliary wall is in the range of about 0.25μm to about 4.5 μm.
 5. The display device according to claim 4, whereinthe organic layer comprises a hole-injecting layer and a light-emittinglayer.
 6. The display device according to claim 5, wherein thehole-injecting layer comprises a material selected from the groupconsisting of poly-3,4-ethylenedioxythiophene and poly styrenesulfonate.7. The display device according to claim 5, wherein the light-emittinglayer comprises a material selected from the group consisting ofpolyfluorene derivatives, poly(p-phenylene vinylene) derivatives,polyphenylene derivatives, poly(N-vinylcarbazole) derivatives, polythiophene derivatives and compounds thereof doped with a perillene grouppigment, rhodamine, rubrene, perillene, 9,10-diphenylanthracene,tetraphenylbutadiene, nile red, cumarine 6, quinacridone.
 8. The displaydevice according to claim 2, wherein the organic layer comprises alight-emitting layer and a hole-injecting layer comprising a materialselected from the group consisting of poly-3,4-ethylenedioxythiopheneand poly styrenesulfonate.
 9. The display device according to claim 2,wherein the organic layer comprises a hole-injecting layer and alight-emitting layer comprising a material selected from the groupconsisting of polyfluorene derivatives, poly(p-phenylene vinylene)derivatives, polyphenylene derivatives, poly(N-vinylcarbazole)derivatives, poly thiophene derivatives and compounds thereof doped witha perillene group pigment, rhodamihe, rubrene, perillene,9,10-diphenylanthracene, tetraphenylbutadiene, nile red, cumarine 6,quinacridone.
 10. The display device according to 1, wherein the heightof the auxiliary wall is about 50% to about 90% of the height of themain wall.
 11. The display device according to claim 10, wherein theheight of the auxiliary wall is in the range of about 0.25 μm to about4.5 μm.
 12. The display device according to claim 11, wherein theorganic layer comprises a light-emitting layer and a hole-injectinglayer comprising a material selected from the group consisting ofpoly-3,4-ethylenedioxythiophene and poly styrenesulfonate.
 13. Thedisplay device according to claim 11, wherein the organic layercomprises a hole-injecting layer and a light-emitting layer comprising amaterial selected from the group consisting of polyfluorene derivatives,poly(p-phenylene vinylene) derivatives, polyphenylene derivatives,poly(N-vinylcarbazole) derivatives, poly thiophene derivatives andcompounds thereof doped with a perillene group pigment, rhodamine,rubrene, perillene, 9,10-diphenylanthracene, tetraphenylbutadiene, nilered, cumarine 6, quinacridone.
 14. The display device according to claim1, wherein the organic layer comprises a light-emitting layer and ahole-injecting layer comprising a material selected from the groupconsisting of poly-3,4-ethylenedioxythiophene and poly styrenesulfonate.15. The display device according to claim 1, wherein the organic layercomprises a hole-injecting layer and a light-emitting layer comprising amaterial selected from the group consisting of polyfluorene derivatives,poly(p-phenylene vinylene) derivatives, polyphenylene derivatives,poly(N-vinylcarbazole) derivatives, poly thiophene derivatives andcompounds thereof doped with a perillene group pigment, rhodamine,rubrene, perillene, 9,10-diphenylanthracene, tetraphenylbutadiene, nilered, cumarine 6, quinacridone.